Digital Commons Network^™

American Splendor, Christina Ehmann

Theses and Dissertations

Artist Statement

My photographs and paintings are reflective of a simpler and slower paced, rural life. This focus is in high contrast to what contemporary urban life often requires. I depict scenes of tranquil landscapes, farm animals, old barns, fields of grasses, and growing crops.

I alter my digital photographic images with computer software. I use various filters that transform color, clarity, and value to give the photographs of nature an intentionally peaceful mood. These photographs are a basis for my paintings where I soften nature’s contours and emphasize tranquility. My desire is that viewers will look at my work …

A Computational Study Of Curvature In The Outflow Graft Of A Continuous Flow Left Ventricular Assist Device, Laura Patterson

Theses and Dissertations

Left ventricular assist devices (LVADs) are an increasingly utilized therapy for end-stage heart failure. Thrombosis within the graft from the pump to the aorta has been documented, but is poorly researched. This study examines the effect of graft geometry, as measured by radius of curvature, bend angle, and diameter, on thrombogenic flow patterns within the graft for a range of flow conditions. It also examines the effect blood properties, including viscosity and density, on these flow patterns. The results indicated that radius of curvature had a powerful effect on thrombogenic flow patterns. Flowrate and bend angle were also influential. The …

Design & Analysis Of A Computer Experiment For An Aerospace Conformance Simulation Study, Ryan W. Gryder

Theses and Dissertations

Within NASA's Air Traffic Management Technology Demonstration # 1 (ATD-1), Interval Management (IM) is a flight deck tool that enables pilots to achieve or maintain a precise in-trail spacing behind a target aircraft. Previous research has shown that violations of aircraft spacing requirements can occur between an IM aircraft and its surrounding non-IM aircraft when it is following a target on a separate route. This research focused on the experimental design and analysis of a deterministic computer simulation which models our airspace configuration of interest. Using an original space-filling design and Gaussian process modeling, we found that aircraft delay assignments …

Electrochemical Studies Of Cerium And Uranium In Licl-Kcl Eutectic For Fundamentals Of Pyroprocessing Technology, Dalsung Yoon

Theses and Dissertations

Understanding the characteristics of special nuclear materials in LiCl-KCl eutectic salt is extremely important in terms of effective system operation and material accountability for safeguarding pyroprocessing technology. By considering that uranium (U) is the most abundant and important element in the used nuclear fuel, measurements and analyses of U properties were performed in LiCl-KCl eutectic salt. Therefore, the electrochemical techniques such as cyclic voltammetry (CV), open circuit potential (OCP), Tafel, linear polarization (LP), and electrochemical impedance spectroscopy (EIS) were conducted under different experimental conditions to explore the electrochemical, thermodynamic, and kinetic properties of U in LiCl-KCl eutectic. The ultimate goal …

Modeling Fluid Interactions With Granular And Fibrous Surfaces, Mana Mokhtabad Amrei

Theses and Dissertations

Understanding the interactions between a body of liquid and a curvy surface is important for many applications such as underwater drag force reduction, droplet filtration, self-cleaning, and fog harvesting, among many others. This study investigates ways to predict the performance of granular and fibrous surfaces for some of the above applications. More specifically, our study is focused on 1) modeling the mechanical stability of the air-water interface over submerged superhydrophobic (SHP) surfaces and their expected drag reduction benefits, and 2) predicting the mechanical stability of a droplet on a fiber in the presence of an external body force. For the …

Design Thinking For The Development Of Formal Operations: A Team-Based Middle School Design Curriculum, Stephanie K. O'Dell

Theses and Dissertations

In this thesis, I propose a team-based design curriculum that aligns with the cognitive development of middle school age students. The ability to think abstractly develops at a specific time in development, according to widely accepted cognitive theory. The middle school years are the launching pad of abstract thinking. At this age, students are also primed for learning through social activity. The design process often includes abstract problem solving challenges, and working within a team structure. These ideas build a foundation for a research question—could a team-based design curriculum in middle school strengthen students’ natural cognitive development by providing opportunities …

Rage And Social Media: The Effect Of Social Media On Perceptions Of Racism, Stress Appraisal, And Anger Expression Among Young African American Adults, Morgan Maxwell

Theses and Dissertations

Recently, social media has become a sociopolitical hotbed for discussions of racism. However, no extant studies have questioned if social media use increases how often African Americans vicariously and/or personally experience discrimination in America. The current study sought to answer this question. By examining the relationships between social media use, general stress, race-related stress, and anger expression, and the mediating role of perceived racism, this study explored if frequent social media use influences young African American adults’: a) perceptions of racism, b) experiences with general and race-related stress, and/or c) expressions of anger. The current study conducted an online survey …

Involvement Of Signal Peptidase I In Streptococcus Sanguinis Biofilm Formation, Jessica Aynapudi

Theses and Dissertations

Biofilm accounts for 65%-80% of microbial infections in humans. Considerable evidence links biofilm formation to oral disease and consequently systemic infections. Eradication of biofilm-associated infections is important. Streptococcus sanguinis, a Gram-positive bacterium, is one of the most abundant species in oral biofilm. It contributes to biofilm development in oral cavities and is one of the recognized causes of infective endocarditis. To study and identify biofilm genes in S. sanguinis, biofilm formation of 51 mutants was compared with the wild type SK36 strain using crystal violet (CV) staining in a microtiter plate. Confocal laser scanning microscopy (CLSM) and image analysis was …

Autonomous Navigation With Obstacle Avoidance For Unmanned Aircraft Systems Using Milp, James A. Devens

Theses and Dissertations

Autonomous coordination among multiple aerial vehicles to ensure a collision free airspace is a critical aspect of today’s airspace. With the rise of Unmanned Aerial Vehicles (UAVs) in the military and commercial sectors, obstacle avoidance in a densely populated airspace is necessary. This thesis investigates finding optimal or near-optimal trajectories in real-time for aircraft in complex airspaces containing a large number of obstacles. The solution for the trajectories is described as a linear program subject to mixed integer constraints, known as a Mixed Integer Linear Program (MILP). The resulting MILP problem is solved in real time using a well-known, public …

High Affinity Block Of Icl,Swell By Thiol-Reactive Small Molecules, Sung H. Park

Theses and Dissertations

Ebselen (Ebs) is considered as a glutathione peroxidase (GPx) mimetic and primarily thought to function by scavenging intracellular reactive oxygen species (ROS). Previous to our work, Deng et al. (2010a) demonstrated complete block of I_Cl,swell with 15 microM Ebs following endothelin-1 (ET-1) induced activation of the current in cardiomyocytes. This block was presumed to take effect mainly via the quenching of ROS. Nonetheless, our work with DI TNC1 astrocytes strongly emphasizes that Ebs might function by an alternative mechanism based on its kinetic profile in blocking I_Cl,swell. Our experiments showed that 45 nM Ebs can fully block …

An Examination Of The Technical And Relational Hypotheses Of Motivational Interviewing In A Sample Of African American Adolescent Girls Seeking Obesity Treatment, Rachel L. Boutte

Theses and Dissertations

Adolescent obesity has increased exponentially over the past three decades in the United States. In response, behavioral interventions have been developed and implemented to address this epidemic; however, treatment adherence is often suboptimal. Motivational interviewing (MI) is a directive, person centered approach to reducing patient ambivalence about change, which has been shown to increase engagement in obesity interventions. The current study investigated the underlying process of MI by exploring two different, but related pathways that explain how change happens (e.g., the technical and relational hypotheses) in the context of a multidisciplinary obesity intervention with African American adolescent girls (N …

Design And Development Of A High-Temperature High-Pressure Rolling Ball Viscometer/Densimeter And Evaluation Of Star Polymer-Solvent Mixtures, Matthew Stanton Newkirk

Theses and Dissertations

Modern automotive applications such as transmission clutch plates, combustion chambers, diesel fuel injector tips, and axle gears and friction plates operate at temperatures that can exceed 250°C and pressures of 40,000 psia. Industrial practice is to add homopolymers and copolymers to base oils to modify bulk fluid viscosity and frictional properties for these demanding applications. However, designing polymeric additives for lubricants and predicting their performance is limited by the lack of available high-temperature high-pressure (HTHP) viscosity and density data needed to test contemporary lubricity models. Thus, a major objective of this thesis is the design, development, and commissioning of a …

Conditional Cardiac-Specific Akap13 Knockout Induces Sex Dependent Biventricular Dilated Cardiomyopathy With Sarcomeric And Mitochondrial Defects, Kimberlyn M. Baig-Ward

Theses and Dissertations

Heart disease is a complex and heterogeneous disease. Notably, studies have demonstrated gender differences in the expression and types of cardiovascular disease, such as dilated cardiomyopathy (DCM), a major underlying cause of heart failure. Previously we showed that loss of A-Kinase Anchoring Protein 13 (Akap13), a unique proto-oncogene and estrogen receptor modulator, resulted in enlarged embryonic hearts, defective cardiac sarcomere formation, and embryonic lethality in mice. Data have also shown cAMP-dependent Protein Kinase A (PKA) to be involved in DCM pathophysiology. Given the established role of AKAP13 in cell signaling, its ability to bind and modulate ligand-activated nuclear hormone …

Hybrid Straintronics-Spintronics: Energy-Efficient Non-Volatile Devices For Boolean And Non-Boolean Computation, Ayan K. Biswas

Theses and Dissertations

Research in future generation computing is focused on reducing energy dissipation while maintaining the switching speed in a binary operation to continue the current trend of increasing transistor-density according to Moore’s law. Unlike charge-based CMOS technology, spin-based nanomagnetic technology, based on switching bistable magnetization of single domain shape-anisotropic nanomagnets, has the potential to achieve ultralow energy dissipation due to the fact that no charge motion is directly involved in switching. However, switching of magnetization has not been any less dissipative than switching transistors because most magnet switching schemes involve generating a current to produce a magnetic field, or spin transfer …

The Relationship Between Program Quality Indicators And Student Achievement In A Braided Prekindergarten Program, Susan L. Flemmons

Theses and Dissertations

The purpose of this study was to determine the relationship between prekindergarten classroom quality indicators and student achievement at the prekindergarten level. Pre-existing data on prekindergarten classroom quality measures and student achievement was utilized. Quality indicators were assessed using the Classroom Assessment Scoring System (CLASS) (Pianta, La Paro, & Hamre, 2008) and student achievement was measured by the end of year results on the Phonological Awareness Literacy Screening (PALS) (Invernizzi, Meier, Swank, & Juel, 2004) and the Bracken School Readiness Assessment end of year results (Bracken, 2007).

A quantitative ex post facto correlational research design was employed to identify relationships …

Identifying Profiles Of Resilience Among A High-Risk Adolescent Population, Anna W. Wright

Theses and Dissertations

The purpose of the present study was to determine whether distinct patterns of adolescent adjustment existed when four domains of functioning were considered. The study included a sample of 299 high-risk urban adolescents, predominantly African American, ages 9-16 and their maternal caregivers. Cluster analysis was used to identify patterns of adjustment. Logistic regression analyses were used to explore whether variations in levels of five theoretically and empirically supported protective factors predicted cluster membership. A four-cluster model was determined to best fit the data. Higher rates of goal directedness and anger regulation coping predicted membership within the highest functioning cluster over …

The Dawn Of New Quantum Dots: Synthesis And Characterization Of Ge1-Xsnx Nanocrystals For Tunable Bandgaps., Richard J. Esteves

Theses and Dissertations

Ge_1-xSn_x alloys are among a small class of benign semiconductors with composition tunable bandgaps in the near-infrared spectrum. As the amount of Sn is increased the band energy decreases and a transition from indirect to direct band structure occurs. Hence, they are prime candidates for fabrication of Si-compatible electronic and photonic devices, field effect transistors, and novel charge storage device applications. Success has been achieved with the growth of Ge_1-xSn_x thin film alloys with Sn compositions up to 34%. However, the synthesis of nanocrystalline alloys has proven difficult due to larger discrepancies (~14%) in …

The Role Of Enteric Glia In Opioid-Induced Constipation, Sukhada Bhave

Theses and Dissertations

Morphine is one of the most widely used drugs for the treatment of pain but its clinical efficacy is limited by adverse effects including persistent constipation and colonic inflammation. Morphine-induced colonic inflammation is facilitated by microbial dysbiosis and bacterial translocation. In this study, we demonstrate that secondary inflammation and persistent constipation are modulated by enteric glia. In chronic morphine treated mice (75 mg morphine pellet/5 days), ATP-induced currents were significantly enhanced in enteric glia isolated from the mouse colon myenteric plexus. Chronic morphine resulted in significant disruption of the colonic epithelium and increased Il-1β in the myenteric plexus. The increase …

Electric Field Controlled Strain Induced Switching Of Magnetization Of Galfenol Nanomagnets In Magneto-Electrically Coupled Multiferroic Stack, Hasnain Ahmad

Theses and Dissertations

The ability to control the bi-stable magnetization states of shape anisotropic single domain nanomagnets has enormous potential for spawning non-volatile and energy-efficient computing and signal processing systems. One of the most energy efficient switching methods is to adopt a system of a 2-phase multiferroic nanomagnet, where a voltage applied on the piezoelectric layer generates a strain in it and the strain is elastically transferred to the magnetostrictive nanomagnet which rotates the magnetization states of the nanomagnet at room temperature via the converse magnet-electric effect. Recently, it has been demonstrated that the magnetization of a Co nanomagnet can be switched between …

Pattern Recognition In Class Imbalanced Datasets, Nahian A. Siddique

Theses and Dissertations

Class imbalanced datasets constitute a significant portion of the machine learning problems of interest, where recog­nizing the ‘rare class’ is the primary objective for most applications. Traditional linear machine learning algorithms are often not effective in recognizing the rare class. In this research work, a specifically optimized feed-forward artificial neural network (ANN) is proposed and developed to train from moderate to highly imbalanced datasets.

The proposed methodology deals with the difficulty in classification task in multiple stages—by optimizing the training dataset, modifying kernel function to generate the gram matrix and optimizing the NN structure. First, the training dataset is extracted …

Propensity Score For Causal Inference Of Multiple And Multivalued Treatments, Zirui Gu

Theses and Dissertations

Propensity score methods (PSM) that have been widely used to reduce selection bias in observational studies are restricted to a binary treatment. Imai and van Dyk extended PSM to estimate non-binary treatment effect using stratification with P-Function, and generalized inverse treatment probability weighting (GIPTW). However, propensity score (PS) matching methods on multiple treatments received little attention, and existing generalized PSMs merely focused on estimates of main treatment effects but omitted potential interaction effects that are of essential interest in many studies. In this dissertation, I extend Rubin’s PS matching theory to general treatment regimens under the P-Function framework. From theory …

The Development Of Bicyclic Peptide Library Scaffolds And The Discovery Of Biostable Ligands Using Mrna Display, David E. Hacker

Theses and Dissertations

Peptides are a promising class of therapeutic candidates due to their high specificity and affinity for cellular protein targets. However, peptides are susceptible to protease degradation and are typically not cell-permeable. In efforts to design more effective peptide drug discovery systems, investigators have discovered that incorporation of non-canonical amino acids (ncAAs) and macrocyclization overcome these limitations, making peptides more drug-like.

In this work, we exploit the promiscuity of wild-type aminoacyl-tRNA synthetases (aaRSs) to ‘mischarge’ ncAAs onto tRNA and ribosomally incorporate them into peptides using a cell-free translation system. We have demonstrated the ability to incorporate five ncAAs into a single …

Considerations In The Provision Of Mental Health Services Toward Arabs, Dalia Khoury

Theses and Dissertations

Existing evidence suggests that disparities exist in the use of mental health services by Arabs in the U.S. While there are likely many factors that contribute, lack of cultural competence of mental health providers is one potentially important barrier for mental health service use among racial/ethnic minorities, including Arabs. The primary purpose of this study was to identify and examine factors related to the development and existence of cultural competence toward Arabs. Variables measuring demographics, professional characteristics, familiarity with Arabs, prior experience and knowledge of Arabs, and readiness for change were tested with a randomly selected sample of mental health …

Social Determinants Of Participation In A Home Visitation Fluoride Varnish Program, James E. Puryear, Tegwyn Brickhouse, Caroline Carrico

Theses and Dissertations

Purpose: The purpose of this study is to examine the social determinants of CHIP (Child Health Investment Partnership) of Roanoke Valley children who participated in the preventive oral health program compared to those who did not.

Methods: This is a retrospective cohort study of children (n=2,425) enrolled in CHIP of Roanoke Valley from September 2008-September 2014. Bivariate analysis and multivariable logistic regression models were used to compare age, gender, race, locality, parents’ education level, age at enrollment, and length of enrollment for oral health program participants versus those who did not participate.

Results: Children who were Hispanic …

Adaptability In A State Of Flux, Yasmeen Suleiman

Theses and Dissertations

“[that] which does not change does not endure” – Henri Bergson

Numbers only quantify the development Qatar is experiencing. In Doha, the city is a physical manifestation of these changes. The general approach to development follows a ‘tear down, build new’ model. Potential value is lost in what is discarded, despite necessity and convenience. This study addresses the topic by dispelling the assumed need to destroy in order to build. In doing so, it examines existing vernacular spaces that are often overlooked. The main application is analyzed through agents of space, such as buildings and the urban environment with varied …

A Two Host Species Stage-Structured Model Of West Nile Virus Transmission, Taylor A. Beebe

Theses and Dissertations

We develop and evaluate a novel host-vector model of West Nile virus (WNV) transmission that incorporates multiple avian host species and host stage-structure (juvenile and adult stages), with both species-specific and stage-specific biting rates of vectors on hosts. We use this model to explore WNV transmission dynamics that occur between vectors and multiple structured host populations as a result of heterogeneous biting rates. Our analysis shows that increased exposure of juvenile hosts results in earlier, more intense WNV transmission when compared to the effects of differential host species exposure, regardless of other parameter values. We also find that, in addition …

Quantitative Analysis Of 5-Chloro-2-Methoxy-N-[2-(4-Sulfamoylphenyl)Ethyl]Benzamide (Glyburide Analogue, Ga) In Mouse Plasma And Whole Blood Using A Micro-Extraction And Liquid Chromatography-Tandem Mass Spectrometry, Ankit Zalavadia

Theses and Dissertations

Pharmacokinetic evaluation of 5-chloro-2-methoxy-N-[2-(4- sulfamoylphenyl)ethyl]benzamide in mouse plasma demanded for a suitable bioanalytical method. No reported bioanalytical method exists to-date that can quantify concentration of this compound in any biological matrix. The purpose of this study was 1) to develop and validate a new bioanalytical method using a micro-extraction and LC-MS/MS to quantify the target analyte in mouse plasma and 2) to partially validate the method in whole blood. A bioanalytical method was developed and validated in both matrices for a linear concentration range of 2-1000 ng/ml. For both matrices, the reverse predicted concentration of calibration standards (-8.95% to 12.16% …

Classification Of Compact 2-Manifolds, George H. Winslow

Theses and Dissertations

It is said that a topologist is a mathematician who can not tell the difference between a doughnut and a coffee cup. The surfaces of the two objects, viewed as topological spaces, are homeomorphic to each other, which is to say that they are topologically equivalent. In this thesis, we acknowledge some of the most well-known examples of surfaces: the sphere, the torus, and the projective plane. We then observe that all surfaces are, in fact, homeomorphic to either the sphere, the torus, a connected sum of tori, a projective plane, or a connected sum of projective planes. Finally, we …

Improving Understandability And Uncertainty Modeling Of Data Using Fuzzy Logic Systems, Dumidu S. Wijayasekara

Theses and Dissertations

The need for automation, optimality and efficiency has made modern day control and monitoring systems extremely complex and data abundant. However, the complexity of the systems and the abundance of raw data has reduced the understandability and interpretability of data which results in a reduced state awareness of the system. Furthermore, different levels of uncertainty introduced by sensors and actuators make interpreting and accurately manipulating systems difficult. Classical mathematical methods lack the capability to capture human knowledge and increase understandability while modeling such uncertainty.

Fuzzy Logic has been shown to alleviate both these problems by introducing logic based on vague …

The Influence Of Client-, Family-, And Therapist-Level Pretreatment Characteristics On Therapist Delivery Of Youth Psychotherapy Treatments, Adriana Rodriguez

Theses and Dissertations

The purpose of this exploratory study was to examine the extent to which pretreatment characteristics influence therapist treatment adherence by using data sampled from a randomized effectiveness trial and an efficacy study. Research suggests that youth-, family-, and therapist-level pretreatment characteristics influence therapist behavior; however, this area is underdeveloped as most studies have focused on externalizing problem areas, family-based approaches, and the use of parent or therapist report to assess for therapist adherence. To date, no research has examined this question with anxiety as the target problem, individual-focused CBT, and with observational therapist adherence data. An observational coding measure, Cognitive-Behavioral …